The field of computer graphics involves rendering various objects so that the objects can be displayed on a computer display for a user. For example, computer games typically involve computer graphics applications that generate and render computer objects for display on a computer monitor or television. Modeling and rendering realistic images is a continuing challenge for those in the computer graphics field. One particularly challenging area within the computer graphics field pertains to the rendering of realistic facial images. As an example, a particular computer graphics application may render a display of an individual engaging in a conversation. Often times, the ultimately rendered image of this individual is very obviously a computer-rendered image that greatly differs from a real individual.
Modeling and rendering realistic faces and facial expressions is a particularly difficult task for two primary reasons. First, the human skin has reflectance properties that are not well modeled by the various shading models that are available for use. For example, the well-known Phong model does not model human skin very well. Second, when rendering facial expressions, the slightest deviation from what would be perceived as “real” facial movement is perceived by even the casual viewer as being incorrect. While current facial motion capture systems can be used to create quite convincing facial animation, the captured motion is much less convincing, and frequently very strange, when applied to another face. For example, if a person provides a sampling of their facial movements, then animating their specific facial movements is not difficult considering that the face from which the movements originated is the same face. Because of this, there will be movement characteristics that are the same or very similar between expressions. Translating this person's facial movements to another person's face, however, is not often times convincing because of, among other things, the inherent differences between the two faces (e.g. size and shape of the face).
Accordingly, this invention arose out of concerns associated with providing improved systems and methods for modeling texture and reflectance of human skin. The invention also arose out of concerns associated with providing systems and methods for reusing facial motion capture data by transforming one person's facial motions into another person's facial motions.